TWI814334B - Film, film roll, film manufacturing method - Google Patents

Abstract

The film of the present invention has a plurality of teardrop-shaped objects at the ends of the film. When the maximum width of the teardrop-shaped objects in the long axis direction is T2 and the maximum width in the short axis direction is T1, the following conditions are satisfied: Expression (1). Formula (1): 1.15≦T2/T1≦1.90

Description

Film, film roll, and film manufacturing method

The present invention relates to a film, a film roll, and a method for manufacturing the film.

Resin films containing cycloolefin resins or (meth)acrylic resins as their main components have good transparency and dimensional stability and are therefore used as optical films such as polarizing plate protective films. Optical films are usually stored or transported in a rolled state from the viewpoint of handleability and manufacturing efficiency.

However, when the film roll is stored or transported in a rolled state, the deformation of the film roll and the adhesion and damage of the films to each other are obvious, the quality of the film is reduced, the waste in the manufacturing process of the polarizer increases, and quality inspections, etc. The increase in the number of workers results in an increase in product prices.

In order to suppress deterioration in quality due to deformation of the film roll, an uneven processing called embossing is usually given to both ends of the film in the width direction (for example, refer to Patent Document 1). On the other hand, the embossed portion formed by the embossing process is easily crushed, and the adhesion of the films to each other may not be sufficiently suppressed.

Regarding this, a method of forming convex portions by coating at both ends in the width direction of a film is also known (for example, refer to Patent Documents 2 and 3). Specifically, there is known a method of casting a film on both ends of a film to form an embossed pattern with a large convex area in a square shape (refer to Patent Document 2), by spraying ink on both ends of the film. Method of forming a convex structure (refer to Patent Document 3). Compared with the uneven structure formed by embossing, the convex portion formed by coating has higher strength and is less likely to be crushed, so it can effectively prevent the films from adhering to each other. [Prior technical literature] [Patent Document]

[Patent Document 1] Japanese Patent Application Publication No. 2016-89110 [Patent Document 2] Japanese Patent Application Publication No. 2012-206312 [Patent Document 3] Japanese Patent Application Publication No. 2010-58311

[Problem to be solved by the invention]

However, the methods of Patent Documents 1 and 2 cannot sufficiently suppress the deformation of the film roll. In addition, the method of Patent Document 3 is required to be further improved in order to meet the high quality requirements for 8K TVs and the like in recent years.

That is to say, the deformation of the film roll and the adhesion of the films to each other are likely to cause increased deviations in optical properties in polarizing plate protective films used in display devices, etc.; deviations in optical properties are likely to cause light leakage in black displays of display devices. . In particular, optical films used in high-resolution display devices such as 8K are required to have less variation in optical properties than ever before, and to reduce quality degradation caused by deformation of the film roll or adhesion of the films to each other. suppressed.

The present invention was made in view of the above-mentioned circumstances, and an object thereof is to provide a film, a film roll, and a method for manufacturing the film in which the deformation of a film roll used for optical films and the adhesion of films are suppressed and the variation in optical characteristics is reduced. [Means used to solve problems]

The above problems can be solved by the following configuration.

The film of the present invention is characterized by having a plurality of teardrop-shaped objects at the ends of the film. When the maximum width of the teardrop-shaped object in the long axis direction is T2 and the maximum width in the short axis direction is T1, the following formula (1) is satisfied, Formula (1): 1.15≦T2/T1≦1.90.

The film roll of the present invention is characterized by rolling a film having a plurality of teardrop-shaped objects at the end of the film. The maximum width of the teardrop-shaped objects in the long axis direction is set to T2, and the maximum width in the short axis direction is set to T2. When the width is T1, the following formula (1) is satisfied, and the intersection M of the long axis and the short axis of the teardrop-shaped object is located upstream in the winding direction from the center on the long axis, Formula (1): 1.15≦T2/T1≦1.90.

The film production method of the present invention is a film production method for producing the film of the present invention, and is characterized in that the teardrop-shaped object is formed by imparting liquid droplets of a resin composition. [Effects of the invention]

According to the present invention, for example, it is possible to provide a film and a film roll that reduce the sticking and roll shape of films such as optical films during storage, and reduce the variation in optical characteristics.

As a result of a thorough investigation of the reason why conventional convex portions (coated knurling portions) were unable to fully suppress the deformation of film rolls, it is not clear, but it is believed that the force exerted on the convex portions during winding was not sufficiently relaxed, resulting in insufficient The uniformly crushed state is caused by being rolled up.

Specifically, during winding, "force in the oblique direction" is applied to the convex portion, which is the "force in the length direction of the film" generated by film transportation and the "force of pressing from above" due to the lamination of the film from directly above. The resultant force is that the film is rolled up while the convex part receives the force in the diagonal direction from the front of the rolling direction (traveling direction). As a result, it is considered that the deformation of the film rolls occurs because the convex portions are unevenly crushed in a state where the force in the oblique direction is not sufficiently relaxed, and are rolled up in a state of uneven contact with the film. The deformation of these film rolls is especially likely to occur in films with lower rigidity.

Based on this speculation, the present invention forms a plurality of convex portions in a row shape and takes into account the force acting from the oblique direction during winding, and sets the top view shape of each plurality of convex portions to a moderately eccentric shape; specifically, the "winding direction" A teardrop shape in which the size of the part on the upstream side (front side in the direction of travel) is moderately larger than the size of the part on the downstream side (rear side in the direction of travel) in the winding direction." This can reduce the poor contact between the films caused by the uneven crushing of the convex portions, and thereby reduce the deformation of the film roll. Specifically, when the film is rolled up, the eccentric part of the teardrop-shaped object is first subjected to the force in the oblique direction, which can fully alleviate the force in the oblique direction during winding, and at the same time, the film is rolled up in a state of uniform contact with the film. (Because the ideal convex shape is in contact with the film), it is considered that the amount of air can be incorporated uniformly and the deformation of the film roll can be suppressed.

These teardrop-shaped objects are formed by applying liquid droplets of the resin composition to the film body (film base). Therefore, unlike conventional embossed portions, they have high strength and are not easily crushed. Therefore, it is easy to further suppress the deformation of the film roll and the adhesion of the films to each other. The structure of the present invention will be described below.

The film of the present invention can be a strip-shaped film or a single-sheet film. In addition, the strip-shaped film can also be rolled into a roll shape to make a film roll. In the following embodiments, a tape-shaped film is used as an example.

1. Film FIG. 1A is a top view of the strip-shaped film of this embodiment, and FIG. 1B is a cross-sectional view along line 1B-1B in FIG. 1A. FIG. 2A is an enlarged top view of the teardrop-shaped object 12 of FIG. 1A , and FIG. 2B is an enlarged cross-sectional view of the teardrop-shaped object 12 of FIG. 1B . FIG. 3 is an enlarged top view of the dotted line portion in FIG. 1A , and FIG. 4 is an enlarged top view of the teardrop-shaped object 12 in FIG. 1A . In addition, hatching of cross sections is omitted in Figures 1B and 2B for easier viewing.

As shown in FIGS. 1A and 1B , the strip-shaped film 10 of this embodiment includes a film base 11 and a plurality of teardrop-shaped objects 12 arranged at both ends in the width direction of the surface (formed by coating).

1-1. Film base 11 The film base 11 is a resin film, preferably a resin film that can be used as an optical film. The resin film contains a first resin composition containing a thermoplastic resin.

(Thermoplastic resin) The thermoplastic resin contained in the resin film is not particularly limited as long as it is suitable for optical films. Examples include cycloolefin resin, (meth)acrylic resin, polyimide, cellulose ester, polyester, and polycarbonate. wait. Among them, from the viewpoint of having good transparency, cycloolefin resins, (meth)acrylic resins, and cellulose esters are preferable, and from the viewpoint of further having low hygroscopicity (high dimensional stability), more preferable are Cycloolefin resin and (meth)acrylic resin.

(Cyclic Olefin Resin) The cycloolefin resin is a polymer containing a structural unit derived from a monomer having a norbornene structure (norbornene monomer). The norbornene-based monosystem is represented by the following formula (A).

R ¹ to R ⁴ in the formula (A) respectively represent a hydrogen atom, a halogen atom, a hydrocarbon group or a polar group.

Examples of halogen atoms include fluorine atoms, chlorine atoms, and the like.

The hydrocarbon group is a hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 4, more preferably 1 or 2. Examples of hydrocarbon groups include alkyl groups such as methyl, ethyl, propyl, butyl, and the like. The hydrocarbon group may further have a divalent linking group containing an oxygen atom, a nitrogen atom, a sulfur atom or a linking group of a silicon atom (for example, a carbonyl group, an imine group, an ether bond, a silicon ether bond, a thioether bond, etc.).

Examples of polar groups include carboxyl groups, hydroxyl groups, alkoxy groups, alkoxycarbonyl groups, allyloxycarbonyl groups, amine groups, amide groups, and connecting groups via methylene groups (-(CH ₂ ) _n -, n is An integer above 1) is a base formed by bonding these bases. Among them, an alkoxycarbonyl group and an aryloxycarbonyl group are preferred, and an alkoxycarbonyl group is more preferred.

Among them, at least one of R ¹ to R ⁴ is preferably a polar group. A cyclic olefin-based resin containing a structural unit derived from a norbornene-based monomer having a polar group is easily dissolved in a solvent when, for example, a solution casting method is used to form a film, and the glass transition temperature of the resulting film is easily increased. On the other hand, in the melt film forming method, a cycloolefin-based resin containing no structural unit derived from a norbornene-based monomer having a polar group may be used.

Moreover, among R ¹ to R ⁴ , both R ¹ and R ² (or both R ³ and R ⁴ ) may be hydrogen atoms.

p in formula (A) represents an integer above 0, preferably 0 or 1. m represents an integer of 0 to 2, and from the viewpoint of improving the heat resistance of the optical film, 1 to 2 is preferred.

Among the norbornene-based monomers represented by formula (A), examples of the norbornene-based monomer having a polar group include the following.

Examples of norbornene-based monomers having no polar group include the following.

The content of structural units derived from norbornene-based monomers is 50 to 100 mol% relative to the total structural units constituting the cycloolefin-based resin.

The cycloolefin-based resin may further include structural units derived from other monomers copolymerizable with structural units derived from norbornene-based monomers. Examples of other copolymerizable monomers include (when the norbornene-based monomer has a polar group) a norbornene-based monomer that does not have a polar group, and cyclobutene, cyclopentene, cycloheptene, and bicyclo Pentadiene and other cyclic olefin monomers that do not have a norbornene skeleton.

The weight average molecular weight Mw of the cycloolefin-based resin is not particularly limited, but is preferably 20,000 to 300,000, more preferably 30,000 to 250,000, and still more preferably 40,000 to 200,000. If the Mw of the cycloolefin-based resin is within the above range, the mechanical properties of the film will be improved without impairing the molding processability.

The Mw of the cycloolefin-based resin can be measured in terms of polystyrene by gel permeation chromatography (GPC). Specifically, it can be measured using HLC8220GPC manufactured by TOSOH Company) and a column (TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL series connection manufactured by TOSOH Company).

The glass transition temperature Tg of the cycloolefin-based resin is generally preferably 110°C or higher, more preferably 110 to 350°C, still more preferably 120 to 250°C. If the Tg of the cycloolefin resin is 110°C or higher, sufficient heat resistance can be easily obtained, and if it is 350°C or lower, thermal deterioration of the cycloolefin resin during molding processing can be suppressed.

Tg can be measured using DSC (Differential Scanning Colorimetry) according to the method of JISK 7121-2012 or ASTMD 3418-82.

((meth)acrylic resin) The (meth)acrylic resin is preferably a polymer containing a structural unit derived from methyl methacrylate. The polymer may further comprise structural units derived from monomers copolymerizable with methyl methacrylate.

Examples of other monomers that can be copolymerized with methyl methacrylate include alkyl esters of (meth)acrylic acid having 1 to 18 carbon atoms other than methyl methacrylate such as 2-ethylhexyl methacrylate; α,β-unsaturated acids such as (meth)acrylic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, etc.; styrenes such as styrene, α-methylstyrene, etc.; horseradish Maleic anhydride; maleimines such as maleimide, N-phenylmaleimine, etc.; glutaric anhydride, etc.

The content of structural units derived from methyl methacrylate is preferably 50 mass % or more, more preferably 70 mass % or more, based on all structural units constituting the above-mentioned polymer.

The Mw of the (meth)acrylic resin is preferably 400,000 to 3,000,000, more preferably 500,000 to 2,000,000. When the Mw of the (meth)acrylic resin is within the above range, sufficient mechanical strength is imparted to the film. The Mw of the (meth)acrylic resin can be measured by the same method as mentioned above.

The Tg of the (meth)acrylic resin is preferably 90°C or higher, more preferably 100 to 150°C. If the Tg of the (meth)acrylic resin is within the above range, the heat resistance of the optical film can be easily improved. The Tg of (meth)acrylic resin can be measured by the same method as mentioned above.

The content of the cycloolefin resin or (meth)acrylic resin is preferably 50 mass% or more, more preferably 70 mass% or more, based on the optical film.

(other ingredients) The optical film may further contain other components as desired. Examples of other ingredients include rubber particles, matting agents, antioxidants, etc.

Rubber particles impart flexibility to the film. The rubber particles are graft copolymers containing rubber-like polymers (cross-linked polymers). Examples of rubber-like polymers include butadiene-based cross-linked polymers, (meth)acrylic acid-based cross-linked polymers, and organosiloxane-based cross-linked polymers. Among them, (meth)acrylic cross-linked polymers are preferred, and acrylic cross-linked polymers are more preferred, in view of the fact that the difference in refractive index with methacrylic resin is small and the transparency of the optical film is not easily damaged. (Acrylic rubber-like polymer).

The matting agent forms unevenness on the surface of the optical film and imparts smoothness. Examples of matting agents include inorganic particles and resin particles. Examples of inorganic particles include fine particles of silica, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, etc., and silica particles are preferred.

The antioxidant is not particularly limited, and for example, hindered phenol antioxidants can be used.

[physical properties] Since the film base 11 is not subjected to embossing processing or laser irradiation, it does not have a thin-walled portion formed by heating and pressing with an embossing roller or melting by laser irradiation. That is, the thickness of the film base 11 is fixed. The thickness of the film base 11 (film thickness) is not particularly limited, but is preferably 5 to 40 μm, more preferably 10 to 40 μm, and still more preferably 15 to 40 μm.

The width X (film width) of the film base 11 is preferably 1000~3200mm, more preferably 2400~2950mm.

The length Y (film length) of the film base 11 is not particularly limited, but is preferably 3000~12000m, more preferably 6000~9000m.

(Phase difference Ro and Rt) The film base 11 has phase differences Ro and Rt depending on its use. For example, the phase difference Ro in the in-plane direction of the film base 11 measured under an environment of 590nm wavelength, 23°C and 55%RH preferably satisfies 40nm≦Ro≦60nm, and the phase difference Rt in the thickness direction preferably satisfies 115nm≦. Rt≦145nm. The film base 11 is suitable as a retardation film combined with a VA liquid crystal cell, for example. Furthermore, if 0nm≦Ro≦10nm and -20nm≦Rt≦20nm, it is suitable as a retardation film combined with an IPS liquid crystal cell.

Ro and Rt are respectively defined by the following formulas. Ro=(nx-ny)×d Rt=((nx+ny)/2-nz)×d (in the formula nx represents the refractive index in the in-plane slow axis direction (the direction with the largest refractive index) of the film base 11, ny represents the refractive index of the film base 11 in the direction orthogonal to the in-plane slow axis, nz represents the refractive index in the thickness direction of the film base 11, d represents the thickness (nm) of the film base 11).

The in-plane slow axis of the film base 11 can be confirmed with an automatic birefringence meter Axo Scan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axo Matrix Corporation).

Ro and Rt can be determined by the following methods. 1) Humidify the film base 11 in an environment of 23°C and 55%RH for 24 hours. The average refractive index of the film base 11 was measured using an Abbe refractometer, and the thickness d was measured using a commercially available micrometer. 2) Use an automatic birefringence meter Axo Scan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axo Matrix Co., Ltd.) to measure the phase difference Ro of the film base 11 after humidity control at a measurement wavelength of 550 nm in an environment of 23°C and 55% RH. and Rt.

1-2. Teardrop shaped object 12 The plurality of teardrop-shaped objects 12 are islands of resin composition arranged at both ends of the surface of the film base 11 in the width direction. Each of the plurality of teardrop-shaped objects 12 has a teardrop shape when viewed from above (refer to FIG. 2A ).

The so-called teardrop shape means having a long axis LA and a short axis SA, and the intersection point M of the long axis LA and the short axis SA of the teardrop shaped object 12 is offset from the center of the long axis LA (does not overlap with the center of the long axis LA). shape (refer to Figure 2A). The long axis LA is preferably along the length direction of the film base 11 (the length direction of the film, y direction), and is more preferably parallel to the length direction (y direction) of the film base 11 . The short axis SA is preferably along the width direction of the film base 11 (the width direction of the film, x direction), and more preferably is parallel to the width direction of the film base 11 (x direction). The y direction is also the conveying direction (traveling direction) of the film during winding. The long axis LA and the short axis SA are preferably orthogonal to each other. The outline of the teardrop shape can be a straight line, a curve, or a combination of these, but a curve is preferred.

In this embodiment, a plurality of teardrop-shaped objects 12 are arranged at both ends in the width direction of the surface of the film base 11 and along the length direction of the film base 11 (see FIG. 2A ). In addition, the plurality of teardrop-shaped objects 12 are each arranged with its long axis LA direction along the length direction of the film base 11 (see FIG. 2A ). When the film width in the width direction of the film base 11 is set to 100%, the end portion of the film surface in the width direction means that the end portion is within 10%, preferably within 5%, of the width direction of the film base 11 area. The teardrop-shaped object 12 may be integrated with the film base 11 or may be a separate object.

Specifically, the teardrop-shaped object 12 preferably satisfies the following formula (1) when the maximum width in the long axis LA direction is T2 and the maximum width in the short axis SA direction is T1. Formula (1): 1.15≦T2/T1≦1.90

If T2/T1 is 1.15 or more, even if an oblique force is applied from the front during winding, the teardrop-shaped object 12 after winding is still in uniform contact with the film, so deformation of the film roll can be suppressed. If T2/T1 is less than 1.9, it will be in uniform contact with the film, so the inhibitory effect of the film roll will not be easily damaged. Based on the same point of view, T2/T1 is preferably 1.3~1.6.

T2/T1 can be adjusted according to the film conveyance speed and drying conditions (drying method, drying temperature), resin concentration of the second resin composition (used to form teardrop-shaped objects), dripping height, surface condition of the film, etc. T2/T1 can be increased by increasing the film conveying speed, lowering the drying temperature, and setting the drying method to hot air drying. Furthermore, if the resin concentration of the second resin composition is appropriately lowered and the dripping height is increased, T2/T1 can be increased.

T1 is not particularly limited, but is, for example, 0.9 to 1.5 mm, preferably 1.0 to 1.2 mm.

When the average distance between the plurality of teardrop-shaped objects 12 in the longitudinal direction (y direction) of the film base 11 is assumed to be T3, T3 and T2 preferably satisfy the following formula (2) (see FIG. 3). Formula (2): T3＜T2

If T3 < T2, when the film is being rolled up while conveying, the front portion of the teardrop-shaped object 12 (the area centered on the intersection M of the long axis LA and the short axis SA) can increase the force that relaxes the oblique direction. Therefore, it can further suppress uneven crushing of the teardrop-shaped object 12 due to oblique force. The difference between T2 and T3 (T2-T3) is not particularly limited, but is, for example, 0.1 mm or more, preferably 0.6 mm or more.

Furthermore, when the width of the film base 11 is represented by X, the following formulas (3) and (4) are more preferably satisfied. Formula (3): 0.0003≦T1/X≦0.0063 Formula (4): 2400mm≦X≦2950mm

From the viewpoint of easily suppressing the deformation of the film roll, the larger the T1/X, the better. Also, when the film is widened, deviations are more likely to occur during film transport than in the past. If T1 / Based on the same point of view, T1/X is preferably 0.0004~0.00051.

Furthermore, assuming that the average distance between the plurality of teardrop-shaped objects 12 in the longitudinal direction (y direction) of the film base 11 is T3 and the length of the film base 11 is Y, it is better to satisfy the following formulas (5) and ( 6). Formula (5): 1.0×10 ⁶ ≦Y/T3≦9.0×10 ⁶ Formula (6): 6000m≦Y≦9000m

From the viewpoint of easily suppressing the adhesion of films to each other, the smaller T3 is, the better (the larger Y/T3 is, the better). In addition, if T3 is too small, the uniformity of the roll shape is easily damaged. If Y/T3 is within the above range, the uniformity of the roll shape can be maintained, and the adhesion (contact) of the films can be highly suppressed. Based on the same point of view, Y/T3 is preferably 3.0×10 ³ ~8.0×10 ³ .

The length X in the width direction of the film is, as mentioned above, preferably 2000~3500mm, more preferably 2400~2950mm. The length Y of the film, as mentioned above, is preferably 500~15000m, more preferably 6000~9000m.

The average interval T3 of the plurality of teardrop-shaped objects 12 in the length direction (y direction) of the film base 11 is not particularly limited as long as it satisfies the above-mentioned ratio range. For example, it is preferably 0.5 to 4 mm, and more preferably 1 to 3 mm. If the average distance T3 of the plurality of teardrop-shaped objects 12 is more than the lower limit, it is easier to appropriately adjust the amount of air contained between the films when the films are rolled into a roll. If it is less than the upper limit, it is easier to adjust the air amount between the films. It is easy to suppress the adhesion of the films caused by the excessive expansion of the average distance T3 of the plurality of teardrop-shaped objects 12 . The average distance T3 between the plurality of teardrop-shaped objects 12 refers to the minimum distance between the ends of the plurality of adjacent teardrop-shaped objects 12 in the length direction (y direction) of the film base 11 . The end of the teardrop-shaped object 12 means the end of the long axis LA.

In the cross-section passing through the vertex (highest point) of the teardrop-shaped object 12 along the width direction (x direction) of the film base 11, the height t of the teardrop-shaped object 12 is 0.5~3 μm (see Figure 2B). If the height t of the teardrop-shaped object 12 is 0.5 μm or more, when the film 10 is rolled into a roll, adhesion of the film bases 11 to each other can be sufficiently suppressed. If the height t of the teardrop-shaped object 12 is 3 μm or less, when the film 10 is rolled into a roll, the absolute amount of crushing of the teardrop-shaped object 12 itself will be reduced, and the film roll will not be easily deformed. Based on the same point of view, the height t of the teardrop-shaped object 12 is preferably 1.0~2.0 μm. Furthermore, the height t of the teardrop-shaped object 12 is the height from the surface of the film base 11 to the vertex of the teardrop-shaped object 12 .

The height t of the teardrop-shaped object 12 is, for example, preferably 1 to 30% of the thickness of the film base 11, and more preferably 2 to 10%.

In the cross section passing through the vertex of the teardrop-shaped object 12 along the width direction (x direction) of the film base 11, the width w of the teardrop-shaped object 12 is not particularly limited, but is preferably 500 to 2000 μm. If the width w of the teardrop-shaped object 12 is 500 μm or more, the support area becomes larger, so the teardrop-shaped object 12 is less likely to be crushed. If the width w is 2000 μm or less, the teardrop-shaped object 12 dries easily when formed by coating with a solution. Furthermore, cooling is easily performed during melt formation, so it is easy to efficiently produce the film of the present invention. Based on the same point of view, the width w of the teardrop-shaped object 12 is preferably 700~1500 μm. The width w of the teardrop-shaped object 12 is the maximum width of the teardrop-shaped object 12 in the above cross-section.

The height t and width w of the teardrop-shaped object 12 can be measured using a laser microscope. As a laser microscope, for example, laser Microscope VK-X1000 manufactured by KEYENEC Corporation can be used. The measurement is performed by measuring the height t and width w of the teardrop-shaped objects 12 within a range of 100 mm in the longitudinal direction (y direction) of the film base 11 in an area where a plurality of teardrop-shaped objects 12 are arranged, and averaging the values. The values are "height t and width w of the teardrop-shaped object 12".

The shape of the teardrop-shaped object 12 is not particularly limited along the cross-section through the vertex of the teardrop-shaped object 12 along the width direction (x direction) of the film base 11, and is usually a circular segment. The so-called arcuate shape is a shape in which both ends of a circular arc or an elliptical arc are connected with a straight line, and examples include semicircles, semiellipses, etc.

The plurality of teardrop-shaped objects 12 are preferably arranged so that the intersection M of the long axis LA and the short axis SA is located at the center of the long axis LA and upstream in the winding direction (refer to FIG. 1A ). Thereby, even if a force in an oblique direction is applied to the teardrop-shaped objects 12, uneven crushing of the plurality of teardrop-shaped objects 12 is suppressed, so deformation of the film roll and adhesion of the films to each other can be suppressed.

The area Su of the teardrop-shaped object 12 on one side of the long axis LA (the area on the winding upstream side) across the center line that passes through the center C on the long axis LA and is orthogonal to the long axis LA, and The area Sd of the area on the other end side of the long axis LA (the area on the winding downstream side) is different. Specifically, it is preferable that Su is larger than Sd (refer to Fig. 4). Specifically, the Su/Sd ratio is preferably 1.2 to 2.0, more preferably 1.3 to 1.6. If Su/Sd is above the lower limit, it is easy to fully relax the force in the oblique direction, so it is easy to suppress the deformation of the film roll. If it is below the upper limit, the supporting properties of the film are less likely to be damaged, and the mutual resistance of the films is easily suppressed. Attachment etc. Su is, for example, 0.5 to 10 mm ² , and Sd is, for example, 0.4 to 5.0 mm ² .

The teardrop-shaped object 12 includes a second resin composition containing a thermoplastic resin.

The thermoplastic resin contained in the teardrop-shaped object 12 may be the same type as the thermoplastic resin included in the film base 11 or may be a different type. However, from the viewpoint of improving the adhesion with the film base 11, it is preferably the same type. . For example, when the thermoplastic resin contained in the film base 11 is a cycloolefin-based resin, the resin contained in the teardrop-shaped object 12 is preferably a cycloolefin-based resin. If the thermoplastic resin contained in the film base 11 and the thermoplastic resin contained in the teardrop-shaped object 12 are of the same type, the adhesion between the teardrop-shaped object 12 and the film base 11 can be improved.

The so-called thermoplastic resins of the same type refer to thermoplastic resins with the same main component monomer (containing the largest component), but the type and content of the copolymerized component monomer, the weight average molecular weight (Mw) and glass transition temperature (Tg) of the resin, etc. The physical properties are different.

The content of the resin is not particularly limited, but is preferably 60% by mass or more, and more preferably 70 to 100% by mass relative to the second resin composition constituting the teardrop-shaped object 12 .

If necessary, the teardrop-shaped object 12 may further contain the same components as the film base 11 (for example, fine particles, etc.). However, from the viewpoint that when the film 10 is rolled up, it is difficult to slide between the teardrop-shaped object 12 and the back surface of the film base 11 and is easily adhered appropriately, the content of the microparticles in the teardrop-shaped object 12 is preferably less than that of the film base. 11 microparticle content, preferably no microparticles.

2. Manufacturing method of thin film The film of the present invention can be obtained through the following steps: 1) casting the first resin composition onto a support to obtain a strip-shaped film base 11, 2) measuring both ends of the surface of the strip-shaped film base 11 in the width direction, A step of adding (dropping) droplets of the second resin composition to form a plurality of teardrop-shaped objects 12 .

1) Regarding the steps to obtain the film base 11 The first resin composition is cast to obtain a strip-shaped film base 11.

The first resin composition can be cast by a melt casting method or a solution casting method. Among them, from the viewpoint that high molecular weight resin can be used, the casting of the first resin composition is preferably carried out by a solution casting method.

That is, the film base 11 can be obtained through the following steps: a step of obtaining a dope (first resin composition) (preparation of the dope); casting the obtained dope onto a support, drying and peeling to obtain a film-like form The step of forming the film (casting); and the step of drying and extending the resulting film (drying and extending).

(Preparation of concentrated liquid) The resin is dissolved in a solvent to prepare a first resin composition.

The solvent used includes an organic solvent (good solvent) that can at least dissolve the resin. Examples of good solvents include chlorine-based organic solvents such as methylene chloride and non-chlorine-based organic solvents such as methyl acetate, ethyl acetate, acetone, and tetrahydrofuran. Among them, methylene chloride is preferred.

The solvent used may further include weak solvents. Examples of weak solvents include linear or branched aliphatic alcohols having 1 to 4 carbon atoms. If the alcohol ratio in the dope is increased, the film-like material will be easily gelled and peeled off from the metal support. Examples of linear or branched aliphatic alcohols having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2nd butanol, and 3rd butanol. Among them, from the viewpoint of stability and drying properties, methanol and ethanol are preferred.

(cast) Next, the obtained first resin composition is streamed onto the support. The first resin composition can be cast by discharging it from a casting mold. The temperature of the first resin composition during casting is usually 15~30°C, preferably room temperature (23°C).

Next, after the solvent in the first resin composition cast on the support is appropriately evaporated (after drying), it is peeled off from the support to obtain a film-like substance.

The residual solvent amount of the first resin composition during peeling is, for example, preferably 25% by mass or more, more preferably 30 to 37% by mass, and still more preferably 30 to 35% by mass. If the residual solvent amount during peeling is 25% by mass or more, the solvent will easily evaporate from the peeled film in one go. In addition, if the amount of residual solvent during peeling is 37% by mass or less, excessive extension of the film due to peeling can be suppressed.

The residual solvent amount of the first resin composition at the time of peeling is defined by the following formula. The same applies to the following. Amount of residual solvent (mass %) = (mass of the first resin composition before heat treatment - mass of the first resin composition after heat treatment)/mass of the first resin composition after heat treatment × 100 In addition, the heat treatment when measuring the residual solvent amount means heat treatment at 140° C. for 15 minutes.

(drying‧extension) Next, the obtained film-like material is dried. Drying can be carried out in one stage or in multiple stages. In addition, drying can be performed while extending if necessary.

Stretching only needs to be carried out according to the required optical properties, but it is preferably stretched in at least one direction, and may also be stretched in two directions that are orthogonal to each other (for example, the width direction (x direction) of the film and the transportation orthogonal thereto) direction (y direction) two-axis extension).

For example, from the viewpoint of using it as a retardation film, the stretching ratio may be 1.01 to 2 times. The stretch ratio is defined as (the size of the film in the stretching direction after stretching)/(the size of the film in the stretching direction before stretching). Moreover, when biaxial stretching is performed, it is preferable to set the above-mentioned stretching magnification for each of the x direction and the y direction. In addition, the in-plane slow axis direction of the film (the direction in which the in-plane refractive index is maximum) is usually the direction in which the extension magnification is maximum.

The drying temperature (extension temperature) during stretching is preferably (Tg-65)℃~(Tg+60)℃, and more preferably (Tg-50)℃~(Tg) when the glass transition temperature of the resin is Tg. +50)℃. If the stretching temperature is above a certain level, the solvent will easily volatilize to an appropriate extent, so it is easy to adjust the stretching tension to an appropriate range. If it is below a certain level, the solvent will not volatilize excessively, so the elongation will not be easily impaired.

The residual amount of solvent in the film-like object at the beginning of stretching is preferably the same as the residual amount of solvent in the film-like object at the time of peeling off, for example, preferably 20 to 30 mass %, more preferably 25 to 30 mass %.

The extension of the membrane in the x direction (TD direction) can be carried out by, for example, fixing both ends of the membrane with clips and pins, and extending the distance between the clips and pins in the direction of travel (tentering method) . The extension of the film in the y direction (MD direction) can be performed by, for example, a method (roller method) in which circumferential speed differences are generated in a plurality of rollers and the difference in circumferential speeds of the rollers is utilized.

From the viewpoint of further reducing the amount of residual solvent, it is preferable to further dry (post-dry) the film obtained after stretching. For example, it is preferable to further dry the film-like object obtained after stretching while being conveyed by a roller or the like (with a certain tension applied).

When the glass transition temperature of the resin is Tg, the drying temperature is preferably (Tg-30) to (Tg+30)°C, and more preferably (Tg-20) to Tg°C. If the drying temperature is above a certain level, it is easy to increase the evaporation rate of the solvent from the stretched film, and thus the drying efficiency is easily improved. If it is below a certain level, it is easy to suppress deformation due to extension of the film.

2) About the steps of forming the teardrop shape object 12 Next, liquid droplets of the second resin composition are applied (dropped) to both ends in the width direction of the surface of the obtained film base 11 to form a plurality of teardrop-shaped objects 12 .

The second resin composition may be a melt or a solution, but from the viewpoint of easy adjustment of shape and size, a solution is preferred.

That is, the teardrop-shaped object 12 can be formed by applying droplets of the second resin composition (rolling solution) containing a resin and a solvent to both ends in the width direction of the film base 11 and then drying.

(Second resin composition) The resin contained in the second resin composition and the resin contained in the dope are of the same type.

The solvent contained in the second resin composition contains at least an organic solvent (good solvent) capable of dissolving the resin. Examples of good solvents include chlorine-based organic solvents such as methylene chloride and non-chlorine-based organic solvents such as methyl acetate, ethyl acetate, acetone, tetrahydrofuran, cyclopentanone, and toluene. Among these, methylene chloride, cyclopentanone, and toluene are preferred from the viewpoint of easily dissolving the cycloolefin-based resin.

The solvent contained in the second resin composition may further include a weak solvent. As the weak solvent, the same weak solvent as that contained in the dope can be used.

In the solution casting method, the resin concentration of the second resin composition is preferably lower than the resin concentration of the first resin composition, more preferably 50% by mass or less of the resin concentration of the first resin composition. Specifically, the resin concentration of the second resin composition is preferably more than 2 mass% and 10 mass% or less, more preferably 3 to 7 mass%. By adjusting the resin concentration of the second resin composition, the height of the teardrop-shaped object 12 can be adjusted. For example, by increasing the resin concentration of the second resin composition, the height of the teardrop-shaped object 12 can be increased.

(given) The second resin composition can be applied by any method, such as a dispenser or an inkjet method, but the inkjet method is preferred because the teardrop shape is easier to adjust.

The temperature of the second resin composition during casting is, for example, 10 to 30°C, preferably room temperature (23°C).

(dry) The second resin composition can be dried by any method, for example, it can be carried out by air drying (including warm air drying) and heating drying by electromagnetic waves (such as heating drying by an infrared (IR) heater). Among them, from the viewpoint of easily adjusting T2/T1 of the teardrop-shaped object 12 to the above range, warm air drying is preferably performed. In addition, in the case of air drying (warm air drying), from the viewpoint of easily adjusting T2/T1 of the teardrop-shaped object 12 within the above range, the air blowing direction is preferably in a direction parallel to the surface of the film, and more preferably Carry out in the opposite direction to the film conveying direction.

The drying temperature is not particularly limited as long as T2/T1 of the teardrop-shaped object 12 can be adjusted to the above range. The drying temperature is preferably higher from the viewpoint of increasing T2/T1. Specifically, when the glass transition temperature of the resin contained in the second resin composition is set to Tg, it is preferably carried out at 40 to (Tg-20)°C. , preferably at 80~(Tg-10)℃. Specifically, 40 to 115°C is preferred, and 80 to 100°C is more preferred.

As mentioned above, T2/T1 can be determined according to the film's conveying speed and drying conditions (drying method, drying temperature), resin concentration of the second resin composition (used to form teardrop-shaped objects), dripping height, surface state of the film, etc. And adjust. By increasing the film conveying speed, lowering the drying temperature, and setting the drying method to hot air drying, T2/T1 can be increased. Furthermore, if the resin concentration of the second resin composition is appropriately lowered and the dripping height is increased, T2/T1 can be increased. The area ratio Su/Sd of the teardrop-shaped object can also be adjusted in the same way.

The average distance T3 between the plurality of teardrop-shaped objects can be adjusted according to the discharge frequency of droplets of the second resin composition, etc. The height of the teardrop-shaped object can be adjusted, for example, by the droplet amount (discharge amount) of the second resin composition.

The obtained strip-shaped film 10 can be rolled into a roll shape along the length direction of the film.

3) Coiling steps The obtained film base 11 is rolled up in the length direction of the film 10 using a winding machine. Thereby, a film roll in which the strip-shaped film 10 is wound around a core can be obtained.

The winding method is not particularly limited, and may be a constant torque method, a constant tension method, a gradually decreasing tension method, etc.

The winding tension when winding the film base 11 is not particularly limited, but can be about 50 to 170N.

(effect) As described above, the film of this embodiment has a plurality of teardrop-shaped objects 12 arranged at both ends in the width direction of the film so that the intersection M of the long axis LA and the short axis SA is located upstream in the winding direction. Next, T2/T1 of each of the plurality of teardrop-shaped objects 12 is adjusted to a specific range. Thereby, during winding, even if an oblique force is applied to the front of the self-moving direction, the oblique force can be relaxed, and the teardrop-shaped object 12 will not be easily crushed unevenly, and the teardrop-shaped object 12 can be in a state of uniform contact with the film ( Ideal convex state) coiling. Therefore, the amount of air can be incorporated uniformly and deformation of the film roll can be suppressed.

(use) When the film 10 is used, the portion where the teardrop-shaped object 12 is formed is removed, and the film 10 is used as an optical film for a display device such as a liquid crystal display device or an organic EL display device. Examples of optical films include polarizing plate protective films (including retardation films and brightness improvement films, etc.), transparent base films, and light diffusion films. Among them, the film 10 is preferably used as a polarizing plate protective film.

[Example of changes] Moreover, although the above embodiment shows an example in which the teardrop-shaped object 12 has a shape as shown in FIG. 2A , it is not limited to this.

FIGS. 5A and 5B are top views of the teardrop-shaped object 12 according to the modified example. The teardrop-shaped object 12 may have a plurality of protruding shapes (refer to FIG. 5A ), or may have a shape such as continuous dots (refer to FIG. 5B ).

FIG. 6A is a top view of a film of another modified example, and FIG. 6B is an enlarged view of the dotted line portion of FIG. 6A . As shown in FIGS. 6A and 6B , the teardrop-shaped object 12 may be in a substantially triangular shape with eccentricity. For example, warm air can be blown vertically from the film conveyance direction (warm air drying) to form a substantially triangular shape.

Furthermore, in the above-mentioned embodiment, the teardrop-shaped object 12 is disposed only on one side of the film base 11 , but the teardrop-shaped object 12 is not limited to this and may be disposed on both sides.

Furthermore, in the above embodiment, the second resin composition for forming the teardrop-shaped object 12 is a solution containing a resin and a solvent. However, the second resin composition is not limited to this and may be a melt.

That is, in the melt casting method, the roll can be obtained through the following steps: 1) delaying the flow of the molten first resin composition, cooling and solidifying to obtain a strip-shaped film base 11, and 2) A step in which droplets of the molten second resin composition are applied to both ends of the strip-shaped film base 11 in the width direction, and then cooled and solidified to form a plurality of teardrop-shaped objects 12 . [Example]

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these.

1. Preparation of film roll <Preparation of film roll 1> (Film production) Cyclic olefin resin G7810 (manufactured by JSR Corporation) (cycloolefin resin containing a structural unit derived from a norbornene monomer represented by the following formula Resin (COP), Tg: 165°C) pellets are supplied to the extruder under a nitrogen environment for melt casting. Next, the melt-cast film is cooled by a cooling roller and then peeled off to obtain a film-like object.

The obtained film was stretched twice in the width direction at 175°C, and then transported while being completely dried by heating at 100°C. The ends were cut off to obtain a film with a thickness of 20 μm, a width of 2260 mm, and a length of 10000 m. The conveying speed of the film is 20m/min.

(Preparation of solution for teardrop-shaped objects) Cycloolefin-based resin G7810 (manufactured by JSR Corporation) was dissolved in the solvent so that the concentration thereof was 5% by mass, and a solution for teardrop-shaped objects was obtained. Dichloromethane is used as the solvent.

(The formation of teardrop-shaped objects) After subjecting the surface of the above-mentioned film to corona treatment and plasma treatment, a solution for imparting teardrop shape using SUPER HI JET produced by Musashi Engineering Co., Ltd. as a dispenser was used on both ends of the treated surface of the film in the width direction. , use an IR heater to dry the film at a temperature of 80°C to form multiple teardrop-shaped objects. Film temperature was confirmed with a thermal imaging camera. By this, a plurality of slightly hilly teardrop-shaped objects with a height of 1.2 μm are formed in rows at both ends of the film surface in the width direction.

Specifically, as shown in FIG. 2A , the teardrop-shaped object is formed at a position 3 mm away from the edge of the film in the width direction of the film (x direction in FIG. 2A ). The top view shape of the teardrop-shaped object is as shown in Figure 2A. The maximum width T1 of the short axis SA is 0.9mm, the maximum width T2 of the long axis LA is 1.2mm, and T2/T1 is 1.33. Furthermore, the average distance T3 between the plurality of teardrop-shaped objects is 1.5 mm. Next, the film on which the teardrop-shaped object is formed is wound on a roll core to obtain a film roll 1 .

＜Preparation of film rolls 2, 3, 23 and 24＞ Film rolls 2, 3, 23, and 24 were obtained in the same manner as film roll 1 except that the average distance (T3) between plural teardrop-shaped objects and T2/T1 were changed to the values shown in Table 1. Furthermore, the average distance (T3) and T2/T1 between the plurality of teardrop-shaped objects are adjusted according to the drying conditions (method, temperature). Specifically, in the film roll 2, the drying temperature is 100°C; in the film roll 3, drying is performed by blowing warm air at 80°C in the opposite direction (horizontal direction) to the film conveyance direction; in the film roll 23, The drying is performed by heating with an IR heater at 120°C (Tg-40°C), and the film roll 24 is dried by blowing drying air at room temperature. The other conditions are the same as those of the film roll 1 .

<Preparation of Film Roll 4> (Preparation of Dope) First, add methylene chloride at a flow rate of 400kg/min and ethanol at a flow rate of 20kg/min in a pressurized dissolving tank. Three minutes after the start of the solvent addition, the cyclic polyolefin resin was added to the pressurized dissolution tank while stirring. Next, 5 minutes after the start of adding the solvent, the microparticle addition liquid was added, and it was heated to 60° C. and completely dissolved while stirring. The heating temperature was raised from room temperature at 5°C/min, and after dissolving for 30 minutes, the temperature was lowered at 3°C/min. Use Azumi filter paper No. 244 (filtration precision 0.005mm) manufactured by Azumi Filter Paper Co., Ltd., filter it at a filtration flow rate of 300L/m ² ‧h and a filter pressure of 1.0×10 ⁶ Pa, and prepare a concentrated liquid with the following composition. Cycloolefin resin G7810 (manufactured by JSR Corporation): 100% by mass, methylene chloride: 380% by mass, ethanol: 20% by mass

(film making) Then, an endless endless belt casting device was used to uniformly cast the obtained concentrated liquid onto the stainless steel belt support body at a temperature of 31°C and a width of 2300mm. Adjust the temperature of the stainless steel belt to 28°C, and set the conveying speed of the stainless steel belt to 30m/min. On the stainless steel belt support, the solvent was evaporated until the amount of residual solvent in the cast (cast) dope reached 30% by mass, and then peeled off from the stainless steel belt support at a peeling tension of 110 N/m to obtain a film. The resulting film is stretched 1.3 times in the transport direction (MD direction) while heating to 120°C using the roller method that utilizes the difference in peripheral speed of the transfer roller, and then stretched in the TD direction while heating to 130°C using the tenter method. 1.65 times. The obtained film was conveyed while being heated at 70°C until it was completely dry, and the ends were cut to obtain a film with a thickness of 20 μm, a width of 2260 mm, and a length of 10000 m. The conveying speed of the film is 20m/min.

The film roll 4 was obtained in the same manner as the film roll 1 except that a plurality of teardrop-shaped objects were formed at both ends in the width direction of the film.

＜Preparation of film rolls 5 and 6＞ Film rolls 5 and 6 were obtained in the same manner as film roll 4 except that at least one of the composition of the dope and the composition of the solution for teardrop-shaped objects was changed as shown in Table 1. Moreover, TAC is cellulose triacetate, and R812 is silica oxide particles.

＜Preparation of Film Roll 7＞ (Preparation of microparticle dispersion) The following ingredients were stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton-Gaulin. Furthermore, in order to make the particle diameter of the secondary particles a specific size, they were dispersed with a mill and then filtered with FINEMET NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle dispersion. R972V (manufactured by Japan Aerosil Corporation): 4% by mass Dichloromethane: 48% by mass Ethanol: 48% by mass

(Preparation of dope and film making) A dope was prepared in the same manner as the film roll 4 except that the fine particle dispersion liquid was further added so that the blending amount of the fine particles was 0.2 mass % based on 100 mass % of the cycloolefin resin G7810 (manufactured by JSR Corporation) to obtain a film.

(Preparation of solutions for teardrop-shaped objects and formation of teardrop-shaped objects) After preparing the teardrop-shaped material solution in the same manner as the film roll 4 except that the above-mentioned fine particle dispersion liquid is added so that the blending amount of the fine particles is 0.1 mass % based on 100 mass % of cycloolefin resin G7810 (manufactured by JSR Corporation), A teardrop-shaped object was formed, and a film roll 7 was obtained.

＜Preparation of Film Roll 8＞ Film roll 8 was obtained in the same manner as film roll 1 except that the height of the teardrop-shaped object was changed as shown in Table 1. The height of the teardrop-shaped object is adjusted by the amount of discharge.

＜Preparation of Film Rolls 9 and 10＞ Film rolls 9 and 10 were obtained in the same manner as film roll 8 except that the thickness of the film or the number of rows of teardrop-shaped objects (at each end of one side) were changed to those shown in Table 1.

＜Preparation of film rolls 11~13＞ Film rolls 11 to 13 were obtained in the same manner as film roll 8, except that the average distance (T3) between plural teardrop-shaped objects was changed as shown in Table 1. The average distance (T3) between plural teardrop-shaped objects is adjusted by the discharge frequency.

＜Preparation of film rolls 14~17＞ Film rolls 14 to 17 were obtained in the same manner as film roll 8 except that the width X of the film was changed as shown in Table 1. Furthermore, for the film 15, the discharge amount was increased, the drying conditions were adjusted (the temperature of the warm air was lowered, the angle at which the warm air was blown was reduced) and the width T1 of the short axis SA of the teardrop-shaped object was further changed as shown in Table 1.

＜Preparation of film rolls 18~21＞ Film rolls 18 to 21 were obtained in the same manner as film roll 8 except that the length Y of the film was changed as shown in Table 1. Furthermore, for some parts, the discharge frequency was adjusted and the average distance T3 between the plurality of teardrop-shaped objects was further changed as shown in Table 1.

＜Preparation of Film Roll 22＞ A film roll 22 is obtained in the same manner as the film roll 12 except that the plan view shape of the teardrop-shaped object is changed as shown in FIG. 5 . The top view shape of the teardrop-shaped object is adjusted by the drying conditions (warm air temperature and the angle of the warm air blowing).

＜Evaluation＞ In addition, the shape of the teardrop-shaped objects of the obtained film rolls 1 to 24 and the deformation of the film roll were evaluated by the following method.

(1) Size and shape of the teardrop-shaped object (height, top view shape, etc.) Use a laser microscope to measure the height t (maximum height) of the teardrop-shaped object in the cross section of the film, the dimensions of the teardrop-shaped object when viewed from above (T1, T2), and the average distance between multiple teardrop-shaped objects (T3). ). As the laser microscope system, laser Microscope VK-X1000 manufactured by KEYENEC Co., Ltd. was used. Specifically, in the area where the teardrop-shaped objects are arranged, the height t of the teardrop-shaped objects and the like are measured over a range of 100 mm in the longitudinal direction of the film, and the average value is taken as the "height t of the teardrop-shaped objects".

(2) Roll failure (deformation of film roll) Double-wrap the rolled film roll with polyethylene sheets, support it on a stand (make the axial direction of the roll core horizontal), and store the two ends of the roll core at 40°C and 80% for 5 days. . Then, open the polyethylene sheet, reflect the illuminated fluorescent tube on the surface of the film roll, and observe its deformation or subtle disorder. Next, evaluation was performed based on the following criteria. ◎: Fluorescent light can be seen immediately 〇: There is only one part visible when the fluorescent lamp is slightly bent, but there is no problem in practice ○△: There are only two parts visible when the fluorescent lamp is slightly bent, but there is no problem in practice. △: There are only 3 parts visible when the fluorescent lamp is slightly bent, but there is no problem in practice. ×: There is a problem in areas where the fluorescent lamp is obviously bent or has mottled reflections. If it is △ or above, it is within the allowable range.

(3) Display quality of 8K LCD device (Production of polarizing plates) Corona treatment is performed on one side of an amorphous polyester film with a thickness of 100 μm. It will contain polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetyl acetate-based modification in a mass ratio of 9:1. The aqueous solution of polyvinyl alcohol (Nihon Synthetic Chemical Industry "GOHSE FIMER Z200"; degree of polymerization 1200, degree of acetyl acetyl modification 4.6%, saponification degree 99.0 mol% or more) is applied to the treated surface at 25°C and dried , to obtain a laminate including an amorphous polyester film base material and a PVA-based resin layer with a thickness of 11 μm.

The obtained laminate was stretched in the length direction with air assistance in an oven at 120°C so that the free end was uniaxially extended 2.0 times, and then sequentially immersed in a 4% boric acid aqueous solution at 30°C for 30 seconds while being transported by a roller. Immerse in dyeing solution (0.2% iodine, 1.0% potassium iodide aqueous solution) at 30°C for 60 seconds. Next, the laminate was immersed in a cross-linking solution (3% potassium iodide, 3% boric acid aqueous solution) at 30°C for 30 seconds while conveying the laminate with a roller, and then immersed in a 4% boric acid, 5% potassium iodide aqueous solution at 70°C. Set the total extension ratio to 5.5 times the length direction and extend the free end uniaxially. Subsequently, the laminated body was immersed in a cleaning solution (4% potassium iodide aqueous solution) at 30°C to obtain a laminated body including an amorphous polyester film base material and a PVA-based polarizing element with a thickness of 5 μm.

(Preparation of active energy ray curable adhesive composition) As an active energy ray curable adhesive composition, the following composition was prepared. N-Hydroxyethylacrylamide: 30 parts by mass Acrylomorpholine: 65 parts by mass Tripropylene glycol diacrylate: 5 parts by mass 2,4-dimethylthioxanthene-9-one (initiator): 1.4 Parts by mass of 2-methyl-1-(4-methylthiophenyl)-2-morpholinylpropan-1-one: 1.4 parts by mass. The above-mentioned curable adhesive composition was applied to the above-mentioned layer with a thickness of about 1 μm. The surface of the polarizing element of the laminate is bonded to the film rolled out from the film roll, and ultraviolet rays with a cumulative light intensity of 1000 mJ/cm ² are irradiated to harden the adhesive. The lamination is performed in such a manner that the slow axis of the film and the absorption axis of the polarizing element are orthogonal to each other.

The amorphous polyester film is peeled off from the laminated body, and the above-mentioned active energy ray curable adhesive composition is coated on the surface of the peeled PVA resin layer. After the film is bonded, ultraviolet rays are irradiated to harden the adhesive. Thereby, a polarizing plate having a polarizing element and the above-mentioned film arranged as a polarizing protective film on both sides of the polarizing element is obtained.

Next, the obtained polarizing plate was used on an 8K liquid crystal display panel to visually evaluate the light leakage spots during black display. Specifically, a roll laminator was used to laminate an acrylic adhesive sheet with a thickness of 20 μm to the film on the surface of the above-mentioned polarizing plate with the slow axis orthogonal to the absorption axis of the polarizing element to obtain adhesive adhesion. layer of polarizing plate.

(Production of liquid crystal display device) Peel off the polarizing plates attached to both sides of the liquid crystal cell of the 60-inch liquid crystal display device 8T-C60BW1 (VA mode) made by Sharp. The adhesive layers of the above-mentioned polarizing plate with adhesive sheets are attached to both sides of the liquid crystal cell respectively. In addition, the directions of the slow axis of the above-mentioned film and the absorption axis of the polarizing element are consistent with the directions in the originally bonded polarizing plate.

(Light leakage during black display) The obtained 8K liquid crystal display device was installed in a dark room, and a full black display was created by external input from the computer. Furthermore, the edges of the four sides are stretched with black tape to create a state where only the black display part is more reliably exposed when viewed from the front. In this state, the light leakage spots were observed and evaluated based on the following criteria. ◎: Almost no light leakage 〇: Very few light leakage spots ○△: Although there are few light leakage spots, there is no problem in practical use. △: Although there are light leakage spots, there is no practical problem ×: There are many light leakage spots, making it unsuitable for practical use. If it is △× or more, it is within the allowable range.

The production conditions and evaluation results of film rolls 1 to 24 are shown in Table 1. In addition, the Su/Sd ratios of films 1 to 3 and 13 are 1.49, 1.28, 1.65 and 1.46 respectively, and the Sd are 0.45mm ² , 0.49mm ² , 0.43mm ² and 0.46mm ² respectively.

As shown in Table 1, film rolls 1 to 22 confirm that the teardrop-shaped object T2/T1 falls within a specific range. Furthermore, it was also confirmed that the area Su of the teardrop-shaped object is larger than Sd. In addition, the film rolls 1 to 22 whose T2/T1 of the teardrop-shaped object fell within a specific range all had fewer roll failures. It can be seen that the display device using the obtained film has less light leakage.

In particular, it was found that by satisfying T3<T2, the deformation of the film roll can be further suppressed (comparison of film 8 and films 10 and 111).

Furthermore, it was found that by satisfying equations (3) and (4), the deformation of the film roll can be further suppressed (comparison of film 14 or 15 and film 16 or 17). Furthermore, it was found that by satisfying equations (5) and (6), the deformation of the film roll can be further suppressed (for example, the comparison between films 19 and 20, etc.).

In contrast, film rolls 23 and 24 that are not in the specific range of T2/T1 both experienced roll failures, which indicates that light leakage occurs when used in display devices.

This application claims priority based on Japanese Patent Application No. 2021-073520 filed on April 23, 2021. The content recorded in the application specification shall be quoted in this application specification. [Industrial availability]

According to the present invention, for example, it is possible to provide a film and a film roll that can suppress sticking and roll shape reduction during storage of films such as optical films, and suppress variations in optical properties.

10: Strip film (film roll) 11: Film base 12: Teardrop shaped object

[Fig. 1A] is a top view of the film of this embodiment, and [Fig. 1B] is a cross-sectional view taken along line 1B-1B in Fig. 1A. [Fig. 2A] is an enlarged top view of the teardrop-shaped object in Fig. 1A, and [Fig. 2B] is an enlarged sectional view of the teardrop-shaped object in Fig. 1B. [Fig. 3] is an enlarged plan view of the dotted line portion of Fig. 1A. [Figure 4] is an enlarged top view of the teardrop-shaped object in Figure 1A. [Fig. 5A and B] are top views of a teardrop-shaped object according to a modified example. [Fig. 6A] is a plan view of a film according to another modification example, and [Fig. 6B] is an enlarged plan view of the dotted line portion in Fig. 6A.

3: Film roll

10: Strip film (film roll)

11: Film base

12: Teardrop shaped object

Claims (18)

A film characterized by having a plurality of teardrop-shaped objects at the ends of the film. When the maximum width of the teardrop-shaped objects in the long axis direction is T2 and the maximum width in the short axis direction is T1, the following is satisfied: Formula (1), formula (1): 1.15≦T2/T1≦1.90. The film of claim 1, wherein the shape of the teardrop-shaped object is a teardrop shape when viewed from above. The film of claim 1 or 2, wherein the film is in a strip shape, and the plurality of teardrop-shaped objects are arranged along the longitudinal direction of the film. The film of claim 3, wherein the long axis direction is along the long side direction of the film. The film according to claim 3, wherein the plurality of teardrop-shaped objects are arranged at both ends in the width direction of the surface of the film. The film of claim 1 or 2, wherein when viewed from above, a region on one end side of the long axis of the teardrop-shaped object is separated from a center line that passes through the center of the long axis of the teardrop-shaped object and is orthogonal to the long axis. When the area is Su and the area of the region on the other end side of the long axis is Sd, Su is different from Sd. The film of claim 3, wherein the average distance between the plurality of teardrop-shaped objects in the longitudinal direction of the film is set to T3, T3 and T2 satisfy the following formula (2), formula (2): T3< T2. For example, the film of claim 3, when the width of the aforementioned film is set to 2950mm. The film of claim 3, wherein the average distance between the plurality of teardrop-shaped objects is set to T3, and the length of the film is set to Y, the following formulas (5) and (6) are satisfied. Formula (5): 1.0×10 ⁶ ≦Y/T3≦9.0×10 ⁶ Formula (6): 6000m≦Y≦9000m. Such as the film of claim 1 or 2, wherein the thickness of the aforementioned film is 10~40 μm. The film of claim 1 or 2, wherein the aforementioned film is an optical film. A film roll characterized by rolling a film having a plurality of teardrop-shaped objects at the ends of the film. The maximum width of the teardrop-shaped objects in the long axis direction is set to T2, and the maximum width in the short axis direction is set to T2. When T1 is used, the following formula (1) is satisfied, and the intersection point M of the long axis and the short axis of the teardrop-shaped object is located further upstream in the winding direction than the center on the long axis, formula (1): 1.15 ≦T2/T1≦1.90. The film roll of Claim 12, wherein the shape of the teardrop-shaped object is a teardrop shape when viewed from above. The film roll of claim 12 or 13, wherein the plurality of teardrop-shaped objects are arranged along the longitudinal direction of the film. The film roll of claim 12 or 13, wherein the long axis direction is along the long side direction of the film. The film roll of claim 12 or 13, wherein when viewed from above, the teardrop-shaped object is wound in the direction of the winding direction across a center line that passes through the center of the long axis of the teardrop-shaped object and is orthogonal to the long axis. When the area of the upstream side is Su and the area of the downstream side in the long-axis winding direction is Sd, Su is larger than Sd. The film roll of claim 12 or 13, wherein the plurality of teardrop-shaped objects are arranged at both ends of the film surface in the width direction. A method for producing a film according to any one of claims 1 to 11, characterized in that the teardrop-shaped object is formed by imparting droplets of a resin composition.

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